1. Field of the Invention
This invention relates generally to photographic apparatus for use in cameras that are adapted to utilize artificial lighting assemblies, e.g., a flashcube, to take flash pictures, and, more particularly, to optical configurations for apparatus for changing the angular light distribution of such artificial lighting assemblies in a preferred manner.
2. Description of the Prior Art
Flashcubes and linear flash arrays are well known commercially available artificial lighting assemblies which combine photoflash lamps with reflectors to illuminate scenes to be photographed. In such assemblies, the photoflash lamp has a principal diameter that is generally not small compared to the focal length of the reflector with which it is associated, typically being at least one-half as large. These assemblies typically do not have the same luminous intensity in all directions, and thus, the scene illumination which they provide is uneven. Characteristically, the intensity of the scene illumination is highest at the center of the scene and generally decreases with increasing distance away from the center. Therefore, subjects in the scene which are located near its edges receive less light than subjects located near the center of the scene, and are therefore darker than they should be in the resultant picture. Except in special situations like portraiture work, where uneven lighting may be desirable for aesthetic reasons, it is obviously more desirable in most amateur picture taking situations to have the scene illuminated as uniformly as possible so that each part of it receives equal emphasis, at least in terms of the illumination falling on it from the artificial lighting assembly.
Those skilled in the photographic arts who have found such uneven scene illumination characteristics objectionable have provided photographic apparatus for use with such artificial lighting assemblies to improve the uniformity of their characteristic illumination distribution to a level of uniformity which they have considered acceptable for their particular purposes.
One such example is disclosed in U.S. No. Des. 218,363 issued to James M. Conner et al on Aug. 11, 1970 and entitled "Light Deflector for a Photographic Camera". The light deflector in this patent comprises a transparent plate having a plurality of elongated, retroreflective type, V-shaped grooves which are separated from one another at equal intervals along the side of the transparent plate which faces the flashcube and operate to modify the light distribution of the flashcube to make it more uniform. While this deflector improves the uniformity of the illumination provided by the flashcube with which it is used, its particular arrangement of V-shaped grooves on the transparent deflector operates to refract light from the flashcube in such a manner so that the overall efficiency of the flashcube in combination with the deflector is reduced thereby reducing the maximum distance at which flash pictures may be taken using this combination.
Another example of an optical device for use with a flashcube is disclosed in U.S. Pat. No. 3,720,145 issued to Bruce K. Johnson et al on Mar. 13, 1973 and entitled "Portrait Camera Having Synchronized Flash Illumination Source". In this patent, a portrait camera is disclosed which has a Fresnel lens mounted in front of the flashcube to focus light from the flashcube into a relatively narrow and limited field angle substantially the same as that of the field of view of the camera. The Fresnel lens of this disclosure operates to generally reduce the angular extent of the flashcube's normal field coverage so that its light output is concentrated within the camera's field of view.
Thus, it is a primary object of the present invention to provide photographic apparatus for use with an artificial lighting assembly, such as a flashcube or a linear flash array, and to modify the distribution in scene illumination intensity provided by such an assembly to a preferred distribution which is more uniform over the field normally covered by the artificial lighting assembly.
Another object is to provide photographic apparatus for improving the uniformity of scene illumination provided by an artificial lighting assembly in an efficient manner.
Other objects of the invention will in part be obvious and will in part appear hereinafter. The invention accordingly comprises the apparatus possessing the construction, the combination of elements, and arrangement of parts which are exemplified in the following detailed disclosure.